1. Field of the Invention
The present general inventive concept relates to a method of detecting free fall, and more particularly, to a method of detecting free fall of a device based on whether the device is periodically accelerated, and an apparatus to detect free fall using the method.
2. Description of the Related Art
Mobile devices, such as cellular phones, personal digital assistants (PDAs), digital cameras, electronic home appliances, and electronic office devices, have become necessities. Mobile devices or storage devices of the mobile devices such as a hard disk drive should be protected from a free fall shock. For example, when a mobile device falls freely, a hard disk drive of the mobile device can be protected by detecting the free fall of the mobile device and parking the head of the hard disk device at a safe position.
In a conventional free fall detecting method, a determination is made that a mobile device falls freely when acceleration of the mobile device is maintained below a predetermined level for a predetermined time. Then, a read/write head of a hard disk drive of the mobile device is moved to a safe region for protecting the read/write head from free fall shocks. That is, the acceleration of the mobile device is monitored, and when the monitored acceleration of the mobile device is kept smaller than a predetermined critical value for a predetermined time, a determination is made that the mobile device falls freely. Conventional methods of detecting free fall of a mobile device for protecting a hard disk drive of the mobile device have been disclosed in articles such as Japanese Patent Laid-Open Publication No. 2005-346840.
However, in the conventional free fall detecting methods, non-free-fall movements (e.g., accelerated or decelerated movements) of a mobile device can be detected as free fall of the mobile device. For example, when a user with a mobile device walks or runs, since the mobile device does not fall freely, a protection operation is not required for the mobile device. However, according to the conventional methods, an erroneous conclusion that the mobile device falls freely can be made. As a result, an unnecessary operation can be performed for protecting a hard disk drive of the mobile device, and thus a user may experience inconvenience due to the unnecessary operation.